Groaning/Growling Noise

I have a groaning/growling noise that gets louder when I turn my A/C up from 1 to 4. Any help would be appreciated. Sounds like this noise is coming from inside the car, and not the engine. Thanks!

1998 Lumina 3.1

Does it do this when the heater is turned on?

I can't remember, but I am fairly positive that it does.

Possibly fan motor, maybe just wornout fan itself. Then again some of them are just noisy. All going from1 to 4 does is increase fan speed.

Yes the fan increases in speed. The sound started out as if something had broken off and was in the way of the fan rotation, but now it just growls and gets louder as you turn the fan up.

Check to see if fan is loose on motor shaft. This prob. will cause what you describe.

Where is this exactly?